Recycling Robots

An engine plant discovers how easy it is to recycle and repurpose existing robots when manufacturing demands change. See table, photo.

Dave Fox, CIM Systems Inc.

09/16/2010

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When it comes to getting the most bang for the buck, especially over the long haul, robots win hands-down over hard automation. Just ask the engineers and operators at the Navistar’s engine plants. The plants produce six- and eight-cylinder medium-duty Diesel engines. Although sections of Navistar’s factories became automated over the years, robotic automation wasn’t a part of the picture until the first robot was installed in the late 1980s.

The company got more serious about robotic automation in 1994, when production demand at the Indianapolis engine plant blew through the 580 engines-per-day limit the production equipment was designed to handle. An evaluation of both cycle times and equipment uptime figures showed the hard automation on the lines was holding up production. By replacing the dedicated cells with robots and improving the bottleneck machines, production numbers more than doubled. In those efforts, the plants have installed approximately 200 ABB robots for material handling, machine tending, adhesive dispensing, deburring, gauging, assembly, painting, and automatic storage and retrieval.

More noteworthy than the robots’ speed and reliability is the fact that many of the individual units have been redeployed at least once. Federally mandated reductions in the allowable emissions from Diesel engines have dramatically reduced the number of years a particular engine model is produced. Consequently, most of the robots currently running production are on their second or third engine program. This is a huge competitive advantage over other manufacturers that use hard automation.

Moving to a new plant

In July, 2009, the Indianapolis engine facility was shut down due to the economic downturn with a dip in demand for Diesel pickup trucks. The remaining V8 production was picked up by the Huntsville engine plant. Many of the robots were shipped from Indianapolis to other Navistar facilities for redeployment.

One of the most significant examples of redeployment involves two ABB IRB 1400 robots, originally implemented on the 7.3 L connecting rod line. These robots were purchased to load and unload a rod assembly machine. The load robot picked up a rod from one conveyor and a cap from another and placed the parts into the assembly machine. The unload robot removed the assembled rod and placed it onto an outgoing conveyor. The cycle time was 7.5 seconds.

The robots were ordered from system integrator CIM Systems in 1997. The original purchase price for the robots, including end-of-arm tooling, programming, and integration, was $66,300 each. The units continued to service the rod assembly machine until a new connecting rod line was installed in July 1999. When removed from service, they had each logged production time of 26,250 hours which means they cost about $2.50 per hour to run. The robots were then removed from the plant and returned to CIM for redeployment.

Teaching old robots new tricks

After removal, the units were returned to CIM where they were re-tooled with adhesive-dispensing heads and re-deployed to replace CNC-based RTV-dispensing equipment on the assembly line. At the time, the plant was using a portable dispensing robot as a backup to three of the CNC machines. The portable robot would be moved via fork truck and used while the primary machine was being repaired. When the rod-line robots became available, the decision was made to use them to replace the CNC equipment.

Since CIM had already designed the adhesive-dispensing tooling for the portable robot, redeployment of the rod-line robots was done over a weekend. The CNC equipment was removed and the robots were placed on the existing bases. Costs for redeployment, including tooling, programming, and integration, were $7,800 each.

The robots continued to service the assembly line until a new line was installed in 2003. The robots were again removed from the plant and returned to CIM for redeployment. By that point, each had now run production for 47,350 hours. Based upon the initial purchase and redeployment costs, spread over the number of production hours, the robots cost approximately $1.60 per hour to run.

Soon after receiving the robots, CIM began to re-tool them with deburring spindles. The Huntsville plant was having an issue with excessive burrs on the new 6.0 L engine block line, so CIM and Navistar engineers decided to use the robots to deburr the block and bed-plate. The new tooling utilized 40,000 RPM spindles, carbide burr bits, and an automatic tool changer.

The veteran robots were installed on the Huntsville block line in July 2003. The only item that was replaced was the SMB battery in the base of the manipulator. The cost for redeployment, including spindles, tool changers, perimeter fencing, programming, and integration, was $61,330 each.

The robots were later re-programmed for the 6.4 L engine, and continue to service the block line. Each robot has now run production for 72,200 hours, which is equivalent to 35 years at 40 hours a week. Based upon the initial and redeployment costs and the number of production hours run, the robots cost approximately $1.88 per hour to run.

Cost calculations per robot

Cost

Hours run

Cost/hour

Initial investment

$66,300

26,250

$2.50

First redeployment

$7,800

21,100

$0.37

Second redeployment

$61,330

24,850

$2.47

Total investment

$135,430

72,200

Avg=$1.88

The only part failure for the robots occurred in 2004 when a base cable on one of the robots was replaced at a cost of $1,875. The estimated cost of power and air for the robot over the 72,200 hours is $21,660 each. This makes the total investment for the pair of robots $316,055, including parts and utilities, or $2.19 per hour. Assuming an average cost of $30.00 per hour for operators, it would have cost $4,332,000 in labor for the same number of production hours.

These two very experienced robots are still running production in the Huntsville engine plant. They were recently reprogrammed to handle a third engine style and reached 100,000 hours of service in early in 2010.

Ensuring long-term success like this requires trying to anticipate future uses for a given robot. This might include specifying a larger payload capacity or reach than the initial project may require, but such thinking improves the potential for redeployment. While many automation projects these days have a fairly short life cycle, the fact that robots can move on to another assignment makes them a better value in the long run.

Dave Fox is President of CIM Systems Inc., the full-service robotic integration company he founded in 1989. CIM Systems provides innovative, common-sense solutions for a wide variety of flexible automation applications throughout North America. Visit www.cimrobotics.com.

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